(363d) Effect of External Vibrations On Non-Isothermal Ice-Nucleation Rates

Effect of
External Vibrations on Non-isothermal Ice-Nucleation Rates

T.J.
Dursch,^1,2 G.J. Trigub,¹ J.F Liu,¹
C.J. Radke,^1,3 A.Z. Weber²

¹
Chemical and
Biomolecular Engineering Department, University of California, Berkeley, CA

²
Environmental
Energy Technology Division, Lawrence Berkeley National Laboratory, Berkeley, CA

³
Earth Sciences
Division, Lawrence Berkeley National Laboratory, Berkeley, CA

AICHE
2013: Session 01C02 Fundamentals of Interfacial Phenomena I

Nucleation stochastically generates aggregates of a new
and more stable phase within a metastable mother phase, capable of growing
rapidly into macroscopic crystallites. Controlled nucleation is critical to the
success of numerous applications, including: manufacturing of bioactive drugs,
thermal energy storage in phase-change materials, zeolite synthesis, and freeze
drying.  Our particular focus lies in ice crystallization during cold-start of
a proton-exchange-membrane fuel cell¹. Commonly, nucleation rates
are obtained from induction-time measurements¹. In many cases,
especially in ice crystallization, large driving forces (e.g., subcoolings of
10-30 °C) are required for sufficiently large nucleation rates and short
induction times. In this work, we examine the effect of an external driving
force, specifically, applied vibrations, on ice-nucleation rates and induction
times.

            Distilled/deionized
(DDI) water, placed in a plexiglass (PMMA) cylinder, is cooled from beneath by
a copper heat exchanger positioned on a vibration generator. Induction times are
obtained using both infrared thermography and thermocouples as a function of
vibration frequency (0 to 50 Hz) and amplitude (1 to 10 mm).  Figure 2 plots 10
repeated induction-time measurements for 30-µL of DDI water at frequencies of 0
(blue), 10 (green), 20 (purple), and 50- Hz (light blue).  Induction times
decrease with increasing vibration frequency (i.e., a factor of 3 from 0 to 50
Hz). Additionally, induction-time Poisson distributions¹ narrow with
increasing vibration frequency, yielding well-controlled nucleation rates. No
theory is currently available to predict the role of vibrations in ice
nucleation.  We find that accounting for work input by mechanical vibrations in
classical nucleation theory provides qualitative agreement with the new
results.

References

 [1]   T.J. Dursch,
M.A. Ciontea, C.J. Radke, A.Z. Weber, Isothermal ice-crystallization kinetics
in the gas-diffusion layer of a proton-exchange-membrane fuel cell, Langmuir 28
(2012) 1222-1234.